Various object detection systems have been proposed to warn motor vehicle drivers of the presence of an object in the path of a movable vehicle. Typically, such warning systems provide a suitable warning signal either audible or visual or both, upon a sensor detecting the presence of an object in the path of the moving vehicle.
The existence of foreign matter or objects on a radar device such as an automotive radar sensor can impact the accuracy and reliability of the radar device. For example, the foreign matter or objects may undesirably block one or more portions of the radar sensor transmit and/or receive antennas and in particular may block portions of the radio frequency (RF) energy propagating to and from the transmit and receive antennas of the radar sensor.
Such blockage may, for example, be the result of an accumulation, over a period of time, of foreign matter or objects in the region of an antenna aperture. Such foreign matter may be caused for example by environmental conditions such as temperature, humidity, ice, rain and the like. Such blockage can degrade, or in extreme cases even prevent, proper operation of the automotive radar sensor. If the foreign matter accumulates over time, there is a corresponding gradual decrease in sensor system performance over time. Since the accumulation is gradual, it is sometimes relatively difficult to detect the existence of antenna blockage due to the gradual accumulation of foreign matter and corresponding gradual decrease in radar sensor performance.
It would, therefore, be desirable to provide a radar device which is capable of detecting blockage. It would also be desirable to provide a radar device which is capable of detecting blockage due to the accumulation of foreign matter, such as mud, ice, snow or the like, on or proximate a radar radome.
According to US 2009/0243912 A1 there is provided a blockage detection process which involves detecting a target within a virtual detection zone, accumulating target-related information while the target is within the virtual detection zone and based on the information determining if a blind spot alert signal was missed. The process further includes recording a time of the miss in response to a decision being made that a blind spot alert signal was missed, and based upon information for each recorded miss, determining whether a blockage condition exists. Hence the blockage detection disclosed in US published patent application number 2009/0243912 A1 requires recording of precise time information. Further, this blockage detection process introduces ambiguity since the blockage detection is based determining that a blind spot alert signal indeed was missed.
Hence, there is still a need for improved blocking detection of a radar device.